The invention relates to telescopic springs, such as gas springs, and particularly to a spring which can perform a switching function in an electric circuit.
In its more specific aspects, the invention is concerned with improvements in telescopic springs of the types disclosed in commonly owned U.S. Pat. No. 3,919,509 and in commonly owned application Ser. No. 39,269, filed May 16, 1979 as a continuation of now-abandoned U.S. application Ser. No. 804,316, filed June 7, 1977. The known springs are being used to advantage for providing a conductive path between a battery or other source of electric current on the body of an automotive vehicle and a current consuming device, such as a lamp, a heater, or a windshield wiper, on a cover mounted on the vehicle body for pivoting movement about a horizontal axis, the spring upwardly biasing the cover. Examples of such covers include the fifth window of a hatch-back passenger car, the trunk lid of a notch-back car, the hood of the motor compartment, and certain tailgates of station waggons. The known devices may automatically interrupt the current supply to the current consuming device in a certain position of the associated cover.
A primary object of this invention is the provision of a telescopic spring operable as an electric switch for applications for which the known springs are not, or not readily, suitable.
Another object is the provision of such a spring which is assembled at relatively low cost from readily available components, yet is sturdy and reliable in its operation.
With these and other objects in view, the spring of the invention includes an outer spring member formed with a cavity therein and an inner spring member connected to the outer spring member for telescoping movement inward and outward of the cavity between two terminal positions. A first portion of the inner spring member is secured in the cavity in both terminal positions, and a second portion projects outward of the cavity in both positions. Fasteners permit the outer spring member and the second portion of the inner spring member to be fastened to respective objects. The inner member is resiliently biased outward of the cavity. A contact element is mounted on one of the spring members, and the inner spring member has a conductive face portion engaged by the contact element during one portion of the movement of the inner spring member. In response to this movement, the contact element is insulated from the conductive face portion during another portion of the movement of the inner spring member. Two electrical connectors outside the cavity are conductively connected to the contact element and to the conductive face portion of the inner spring member respectively.